The present invention relates to roll-reefing for jib sails and more particularly to a roll-reefing system which maintains an aerodynamically efficient sail shape for a jib which is partially reefed.
Various roll furling systems have been known heretofore which effectively provide for furling of a jib sail by wrapping thereof around a jib stay or other torsion element. Most such commercially available systems however provide only furling, that is, the sail may be completely wrapped or wound up so as to be effectively stored while out of use. Certain attempts have also been made to provide roll reefing for jib sails, e.g. systems in which the jib may be partially rolled up on a luff element so as to provide a reduced sail area suitable for sailing in heavier winds. These latter attempts, however, have typically met with quite limited success, either due to insufficient torsional rigidity in the jib luff element or due to a wrapping operation which produces a badly distorted sail shape, typically accompanied by extreme tension on the foot and leach tapes.
In accordance with one aspect of the present invention, it has been recognized that the usual poor sail shape and high tension on the leach and foot tapes arises due to the winding of the head and foot of the jib simultaneously with the main portion of the jib luff. The necessarily increased thickness of the taped hems along the leach and foot causes the material in these regions to bunch and draw more rapidly, thereby greatly increasing the tension along these edges. This tension then creates a baggy or full bellied sail. As is understood by those skilled in the art, a full bellied sail is just the opposite of what is desired for increased wind speed. Rather, a flatter sail would be more appropriate.
Prior attempts to remedy or compensate for this problem have typically involved the use of a luff element which is thicker near its middle than toward the ends, the purpose of the thicker central portion being to provide an increased linear rate of wrapping of the belly of the sail, as compared with the head and foot. One example of such a system is that shown in U.S. Pat. No. 3,938,460. Despite being highly complex and necessarily involving luff elements of tapered or graduated sizes, such approaches have also met with very limited success since it has been almost impossible to exactly match the taper of the luff element with the drawing speed required to maintain a desirable sail shape.
Among the several objects of the present invention may be noted the provision of apparatus for roll-reefing a jib sail; the provision of such apparatus which will maintain an efficient and effective jib sail shape over a wide range of settings; the provision of such a system which does not require the use of tapered or graduated luff elements for wrapping the luff of the jib; the provision of such a system which avoids undue tension in the leach and foot of a jib sail being reefed; the provision of such a system which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.